I'm 90kg and run 100 front and rear (+/1 5psi depending on when I last blew them up), any more is pointless unless you're significantly heavier and if you're lighter then go with a bit less for slightly added comfort.
I use 25's over 23's apart from on the winter bike at the rear where I can't fit a 25 under the mudguard.
Tread is another oft-debated one, I think most people agree siping for wet weather performance is pointless as aqua-planing is a non-issue. File treads though I can possibly increasing traction as they squirm under load when cornering - I've not seen it tested and presumably the effect is lost pretty quickly when they start to wear. Personally I always use slicks